Evaluation method of semiconductor layer, method for fabricating semiconductor device, and storage medium

ABSTRACT

Measurement light, which has been emitted from a Xe light source (20) and then linearly polarized by a polarizer (21), is made to be incident at a tilt angle on a region in a silicon substrate (11) with crystallinity disordered by the implantation of dopant ions. And the spectra of cosΔ and tan ψ are measured with a variation of the measurement light, where Δ is a phase difference between respective components in p and s directions as to the light reflected as an elliptically-polarized ray, and ψ is a ratio between the amplitudes of these components. By correlating in advance the spectral patterns of cosΔ and so on with the thickness of an amorphous region through a destructive test or the like, or by paying special attention to characteristic parts of the patterns of cosΔ and so on, the thickness or the degree of disordered crystallinity of the amorphous region is estimated. Also, since a variation in the thickness of the amorphous region can be identified based on a variation of cosΔ before and after a heat treatment, a temperature of the heat treatment can be sensed based on the variation of the thickness. Thus, an evaluation method allowing for nondestructive estimation of the thickness and the degree of disorder of a region, having crystallinity disordered by implanting dopant ions into a semiconductor region at a high level, can be provided.

TECHNICAL FIELD

The present invention relates to a method for optically evaluating thecharacteristic of an amorphous region with crystallinity disordered bydopant ions implanted at a high level, a method for measuring atemperature and a method for fabricating a semiconductor deviceutilizing such evaluation, and a storage medium used for automaticallymaking the evaluation.

BACKGROUND ART

In a fabrication process of a semiconductor device such as a transistor,when source/drain regions for a MOSFET, an emitter diffusion layer for abipolar transistor and so on are formed, for example, ion implantationfor accelerating and implanting ions such as P, As and B into asemiconductor substrate, a polysilicon layer or an amorphous siliconfilm has heretofore been utilized as a means for accurately controllingdoping level of the dopant, depth of a region to be doped and the like.Recently, in order to meet a demand for miniaturization of semiconductordevices, the dopant concentration and thickness of a region formed bythe ion implantation need to be controlled even more precisely.

For example, it is known that, when silicon atoms are scattered out ofthe normal sites thereof by dopant ions implanted into a singlecrystalline layer, an amorphous region is formed by these recoil siliconatoms. As a means for measuring the thickness and the like of such anamorphous region formed by these recoil silicon ions, Rutherfordbackscattering spectrometry (RBS) and the photograph of a cross sectiontaken with a transmission electron microscope (TEM) are conventionallyadopted.

Ion implant energy and dose of dopant ions implanted into a siliconsubstrate are conventionally estimated by 4-terminal sheet resistancemeasurement or thermal wave method. Similarly, the uniformity of thedopant concentration of an ion implanted layer formed on a siliconsubstrate in a silicon wafer by the ion implantation is also estimatedby 4-terminal sheet resistance measurement or thermal wave method.

On the other hand, ellipsometry, obtaining information such as complexrefractive index and thickness by making linearly-polarized lightincident on the surface of a substrate at a tilt angle and measuring anelliptical shape of elliptically-polarized light reflected from thesubstrate surface, is known as a simple optical evaluation method.

Problems to be Solved

However, when these evaluation methods are applied to thecharacterization during the actual fabrication process of asemiconductor device, the following problems arise. And it has beendifficult to evaluate whether or not the implantation conditions areappropriate for a region implanted with ions at a high level, inparticular.

First, the RBS and the TEM are destructive test methods, and hence arenot suitable for evaluation in the production line of semiconductordevices.

Furthermore, when a region implanted with a dopant at a high level isevaluated by the sheet resistance measurement, the measurement isconsiderably affected by a heat treatment because accelerated diffusionis locally caused due to the damage resulting from the ion implantation.Accordingly, it is impossible to evaluate the ion implantationconditions by themselves.

In accordance with the thermal wave method, the ion implant energy andthe concentration of implanted ions are estimated by measuring a damagein an implanted layer. In a region implanted with an impurity at a highlevel, however, it is difficult to identify the difference in implantdoses, because the degree of the damage reaches a saturation region ofdetection sensitivity. In addition, since a value detected is not anabsolute magnitude but a relative value, high detection sensitivitycannot be expected as to such a region implanted at a high level.

The present invention was made in view of these problems. The object ofthe present invention is to provide an evaluation method of asemiconductor layer, by which the thickness of an amorphous region,having crystallinity disordered by dopant ions implanted into thesemiconductor layer at a high level, and the distribution of thethicknesses in the surface of a substrate can be nondestructivelyestimated with satisfactory reproducibility. Another object of thepresent invention is to provide a method for fabricating a semiconductordevice utilizing this evaluation method of a semiconductor layer. Stillanother object of the present invention is to provide a storage mediumfor making a computer execute the evaluation of a semiconductor layer.

DISCLOSURE OF INVENTION

In order to accomplish this object, according to the present invention,a parameter regarding a complex refractive index and the spectralpattern thereof obtained by a spectroscopic ellipsometry are utilizedfor estimating a physical quantity of an amorphous region.

An evaluation method of a semiconductor layer according to the presentinvention includes the steps of: i) making linearly-polarizedmeasurement light incident on the surface of the semiconductor layer ata tilt angle defined with respect to a normal crossing the surface atright angles, the semiconductor layer including an amorphous region withcrystallinity disordered by dopant ions implanted into a substrate, themeasurement light being tilted relative to p and s directions in a planevertical to the optical axis thereof, the p direction being defined byan intersection between the plane vertical to the optical axis and aplane containing incident and reflected rays, the s direction beingvertical to the p direction in the plane vertical to the optical axis;ii) deriving at least cosΔ as to the reflected ray of the measurementlight reflected as an elliptically-polarized ray from the semiconductorlayer, where Δ is a phase difference between p and s components; iii)measuring the spectrum of at least the cosΔ in accordance with avariation in the wavelength of the measurement light; and iv) estimatinga physical quantity of the amorphous region based on at least thespectrum of the cosΔ.

In accordance with this method, if the wavelength of the measurementlight, detected as an elliptically-polarized ray, is varied, then cosΔ,one of the parameters regarding the complex refractive index of thesemiconductor layer, and other parameters are obtained. In addition, thespectra of cos Δ and so on are obtained as information on the thicknessand film quality of the amorphous region. As a result, the physicalquantity of the semiconductor layer, subjected to the ion implantation,can be estimated nondestructively.

In the evaluation method of a semiconductor layer, the transparency,presence or absence and thickness of the amorphous region can beestimated in the step iv).

When the thickness of the semiconductor layer is estimated, the methodfurther includes the step of preparing a correlation between thethickness of the amorphous region and at least the spectrum of cosΔ. Inthe step iv), the thickness of the amorphous region in the semiconductorlayer can be determined by reference to the correlation about at leastthe spectrum of cosΔ obtained in the step ii).

In the step of preparing the correlation, a relationship between implantenergy and the thickness of the amorphous region and a relationshipbetween the spectrum of cosΔ and implant energy are prepared as firstand second correlations, respectively, with regard to each particularion implant dose. And in the step iv), after the implant energy of theions implanted into the semiconductor layer has been obtained byreference to the second correlation about the spectrum of cosΔ obtainedin the step ii), the thickness of the amorphous region in thesemiconductor layer can be determined by reference to the firstcorrelation about the implant energy obtained.

Alternatively, in the step of preparing the correlation, a relationshipbetween an ion implant dose and the thickness of the amorphous regionand a relationship between the spectrum of cosΔ and an ion implant doseare prepared as first and second correlations, respectively, with regardto each particular implant energy. And in the step iv), after theimplant dose of the ions implanted into the semiconductor layer has beenobtained by reference to the second correlation about the spectrum ofcosΔ obtained in the step ii), the thickness of the amorphous region inthe semiconductor layer can be determined by reference to the firstcorrelation about the ion implant dose obtained.

In accordance with these methods, if the first and second correlationsare prepared, the thickness of the amorphous region can be estimatednondestructively and with high reproducibility by reference to thesecorrelations about the spectrum of cosΔ obtained through the measurementby the spectroscopic ellipsometry.

Furthermore, in the step of preparing the correlation, a relationshipbetween implant energy and the thickness of the amorphous region isprepared as a first correlation with regard to each particular ionimplant dose, and a relationship between a wavelength corresponding to alocal maximum of cos Δ within a predetermined wavelength region of thespectrum of cosΔ and implant energy is prepared as a second correlation.The wavelength region is defined by making the ion implant dose constantand the implant energy variable. And in the step iv), after the implantenergy of the ions implanted into the semiconductor layer has beenobtained by reference to the second correlation about the spectrum ofcosΔ obtained in the step ii), the thickness of the amorphous region inthe semiconductor layer can be determined by reference to the firstcorrelation about the implant energy obtained.

Alternatively, in the step of preparing the correlation, a relationshipbetween an implant dose and the thickness of the amorphous region isprepared as a first correlation with regard to each particular implantenergy, and a relationship between a wavelength corresponding to a localmaximum of cos Δ within a predetermined wavelength region of thespectrum of cosΔ and an implant dose is prepared as a secondcorrelation. The wavelength region is defined by making the implantenergy constant and the implant dose variable. And in the step iv),after the implant dose of the ions implanted into the semiconductorlayer has been obtained by reference to the second correlation about thespectrum of cosΔ obtained in the step ii), the thickness of theamorphous region in the semiconductor layer can be determined byreference to the first correlation about the ion implant dose obtained.

In accordance with these methods, if the first and second correlationsare prepared, the thickness of the amorphous region can be estimatednondestructively and with high reproducibility by reference to thesecorrelations about the spectrum of cosΔ obtained through the measurementby the spectroscopic ellipsometry.

According to these two methods, the thickness of the amorphous regioncan be detected easily and rapidly.

By performing the steps i) to iv) on a plurality of amorphous regions inthe semiconductor layer, the distribution of thicknesses of theamorphous regions in the semiconductor layer can be estimated.

Furthermore, in accordance with this evaluation method of asemiconductor layer, the following specific information on the physicalquantity of the amorphous region can be obtained. In the step iv), thedegree of recovery of the amorphous region responsive to ion beams canbe estimated. Alternatively, in the step iv), the performance ofimplanters can be evaluated based on at least the spectra of cosΔ of twoamorphous regions formed using two different implanters on the sameimplant conditions.

The evaluation method of a semiconductor layer may further include thesteps of: deriving tanψ as to the reflected ray of the measurementlight, where ψ is a ratio of the amplitude of a p component to that ofan s component; and measuring the spectrum of the tanψ with thewavelength of the measurement light varied. In the step of estimatingthe physical quantity of the amorphous region, the physical quantity ofthe amorphous region can be estimated with the shape of the spectrum ofthe tan ψ taken into consideration.

In accordance with this method, more accurate information on theamorphous region can be obtained based on cosΔ and tan ψ, which are twoparameters regarding the complex refractive index.

In the evaluation method of a semiconductor layer, a first thickness ofthe amorphous region may be determined by performing the steps i)through iv) on the semiconductor layer before a heat holding process isconducted. The method may further include the steps of: determining asecond thickness of the amorphous region by performing the steps i)through iv) on the semiconductor layer after the heat holding processhas been conducted on the semiconductor layer; and measuring atemperature of the heat holding process based on a recovery rate derivedfrom the first and second thicknesses of the amorphous region and a timeof the heat holding process.

In accordance with this method, the temperature at the upper surface ofa substrate can also be sensed unlike a method using a wafer providedwith a temperature sensor. In addition, the temperature can be measuredin a substantially unlimited range.

The evaluation method of a semiconductor layer may further include thestep of finding a correlation between a temperature of the heat holdingprocess conducted at a temperature equal to or lower than 450° C. and adecrease in thickness of an amorphous region. In the step iv), thetemperature of the heat holding process can be measured based on thecorrelation.

In accordance with this method, the evaluation can be done rapidly.

In the evaluation method of a semiconductor layer, the temperature ofthe heat holding process may be measured as to each of a plurality ofamorphous regions in the substrate. And the distribution of temperaturesin the substrate or in a processing system can be measured based on thetemperatures held at the amorphous regions.

In accordance with this method, more detailed information can beobtained, and therefore, the results of evaluation are applicable tofine adjustment in conditions for various types of heat treatments, forexample.

A first method for fabricating a semiconductor device is a method forfabricating a semiconductor device on a semiconductor layer in asubstrate. The method includes the steps of: i) forming an amorphousregion with crystallinity disordered by implanting dopant ions into thesemiconductor layer; ii) making linearly-polarized measurement lightincident on the surface of the semiconductor layer, where the amorphousregion has been formed, at a tilt angle defined with respect to a normalcrossing the surface at right angles, the measurement light being tiltedrelative to p and s directions in a plane vertical to the optical axisthereof, the p direction being defined by an intersection between theplane vertical to the optical axis and a plane containing incident andreflected rays, the s direction being vertical to the p direction in theplane vertical to the optical axis, and measuring at least the spectrumof cosΔ in accordance with a variation in the wavelength of themeasurement light as to the reflected ray of the measurement lightreflected as an elliptically-polarized ray from the semiconductor layer,where Δ is a phase difference between p and s components; and iii)estimating a physical quantity of the amorphous region based on at leastthe spectrum of the cosΔ obtained in the step ii).

The first method for fabricating a semiconductor device may furtherinclude the step of preparing a correlation between the thickness of theamorphous region and at least the spectrum of cosΔ. In the step iii),the thickness of the amorphous region in the semiconductor layer can bedetermined by reference to the correlation about at least the spectrumof cosΔ obtained in the step ii).

In accordance with this method, if the wavelength of the measurementlight, detected as an elliptically-polarized ray, is varied, then cosΔ,one of the parameters regarding the complex refractive index of theamorphous region, and other parameters can be obtained. In addition, theshapes of the spectra of cosΔ and so on are obtained as information onthe physical quantity of the amorphous region, i.e., the degree ofdisorder, the thickness of the amorphous region and the like.Accordingly, by nondestructively estimating the physical quantity of theamorphous region with crystallinity disordered owing to the ionimplantation, it can be determined whether or not ion implantationconditions are appropriate. And if the ion implantation conditions areinappropriate, then these conditions can be modified.

The first method for fabricating a semiconductor device may furtherinclude the step of changing ion implantation conditions for the stepii) based on the result of evaluation of the physical quantity of theamorphous region obtained in the step iii).

In accordance with this method, the fabrication process can be improvedby feeding back the measurement results obtained by the spectroscopicellipsometry to the ion implantation process step.

The first method for fabricating a semiconductor device may furtherinclude the step of determining whether or not the substrate includingthe amorphous region is acceptable based on the result of evaluation ofthe physical quantity of the amorphous region obtained in the step iii).

In accordance with this method, it is possible to determine whether thefinal product will be good or bad during the fabrication process ofsemiconductor devices. Accordingly, the throughput can be improved bycanceling subsequent process steps on defective products or byadditional implantation.

A second method for fabricating a semiconductor device according to thepresent invention is a method for fabricating a semiconductor device ona semiconductor layer in a substrate. The method includes the steps of:i) forming an amorphous region with crystallinity disordered byimplanting dopant ions into the semiconductor layer; ii) conducting aprocess of holding the temperature of the amorphous region at apredetermined temperature; iii) making linearly-polarized measurementlight incident on the surface of the semiconductor layer at a tilt angledefined with respect to a normal crossing the surface at right angles,the measurement light being tilted relative to p and s directions in aplane vertical to the optical axis thereof, the p direction beingdefined by an intersection between the plane vertical to the opticalaxis and a plane containing incident and reflected rays, the s directionbeing vertical to the p direction in the plane vertical to the opticalaxis, and measuring at least the spectrum of cosΔ in accordance with avariation in the wavelength of the measurement light as to the reflectedray of the measurement light reflected as an elliptically-polarized rayfrom the semiconductor layer, where Δ is a phase difference between pand s components; and iv) estimating a physical quantity of theamorphous region based on at least the spectrum of cosΔ obtained in thestep iii).

In accordance with this method, if the wavelength of the measurementlight, detected as an elliptically-polarized ray, is varied, then cosΔ,one of the parameters regarding the complex refractive index of theamorphous region, and other parameters can be obtained. In addition, theshapes of the spectra of cosΔ and so on are obtained as information onthe physical quantity of the amorphous region, i.e., the degree ofdisorder, the thickness of the amorphous region and the like.Accordingly, by nondestructively estimating the physical quantity of thesemiconductor layer with crystallinity disordered owing to the ionimplantation, it can be determined whether or not conditions for asubsequent heat treatment are appropriate. And if the heat treatmentconditions are inappropriate, then these conditions can be modified.

The second method for fabricating a semiconductor device may furtherinclude the step of preparing a correlation between the thickness of theamorphous region and at least the spectrum of cosΔ. In the step iv), thethickness of the amorphous region in the semiconductor layer can bedetermined by reference to the correlation about at least the spectrumof cosΔ obtained in the step ii).

In accordance with this method, since the thickness of the amorphousregion can be found, it is possible to determine how far activation hasreached during a process such as annealing. In addition, the level ofappropriate conditions for annealing a substrate can also be determined.

The second method for fabricating a semiconductor device may furtherinclude the steps of: estimating the thickness of the amorphous regionprior to the step ii) by performing the same process steps as the stepsiii) and iv) posterior to the step i) and prior to the step ii); andobtaining a variation in the thickness of the amorphous region beforeand after the step ii) is performed.

In the second method for fabricating a semiconductor device, in the stepiv), a reflection factor of the measurement light reflected from theamorphous region may be calculated based on a ratio between theintensity of the incident and that reflected rays of the measurementlight. And film quality of the amorphous region can be evaluated basedon the reflection factor.

A third method for fabricating a semiconductor device according to thepresent invention is a method for fabricating a semiconductor device ona semiconductor layer in a substrate. The method includes the steps of:i) forming an amorphous region with crystallinity disordered byimplanting dopant ions into the semiconductor layer; ii) conducting aprocess of holding the temperature of the amorphous region at apredetermined temperature; iii) making linearly-polarized measurementlight incident on the surface of the semiconductor layer at a tilt angledefined with respect to a normal crossing the surface at right angles,the measurement light being tilted relative to p and s directions in aplane vertical to the optical axis thereof, the p direction beingdefined by an intersection between the plane vertical to the opticalaxis and a plane containing incident and reflected rays, the s directionbeing vertical to the p direction in the plane vertical to the opticalaxis, and measuring at least the spectra of cosΔ before and after theprocess in the step ii) is performed as to the reflected ray of themeasurement light reflected as an elliptically-polarized ray from thesemiconductor layer, where Δ is a phase difference between p and scomponents; iv) measuring a variation in the thickness of the amorphousregion before and after the process in the step ii) is performed basedon at least the variation in the spectrum of cosΔ; and v) measuring atemperature of the heat holding process based on a recovery ratecalculated based on the variation in the thickness of the amorphousregion before and after the process is performed and a time of the heatholding process.

The third method for fabricating a semiconductor device may furtherinclude the step of preparing a correlation between a temperature of theheat holding process conducted at a temperature equal to or lower than450° C. and a decrease in thickness of the amorphous region. In the stepiv), the temperature of the heat holding process can be measured basedon the correlation.

The present invention also provides a storage medium for making acomputer automatically execute the procedures of the evaluation methodof a semiconductor layer.

A first storage medium according to the present invention is a storagemedium used for estimating a physical quantity of a semiconductor layerbased on at least the spectrum of cosΔ in accordance with a variation inthe wavelength of measurement light after a process of holding thetemperature of the semiconductor layer at a predetermined temperaturehigher than room temperature has been conducted. The amorphous region islocated in the semiconductor layer in a substrate. The crystallinity ofthe amorphous region has been disordered by the implantation of dopantions into the substrate. The measurement light has been incident on thesemiconductor layer at an angle tilted relative to p and s directions ina plane vertical to the optical axis thereof and then reflected as anelliptically-polarized ray from the semiconductor layer. The p directionis defined by an intersection between the plane vertical to the opticalaxis and a plane containing incident and reflected rays. The s directionis vertical to the p direction in the plane vertical to the opticalaxis. Δ is a phase difference between p and s components as to thereflected ray. The storage medium stores a program for making a computerexecute the procedures of: i) storing a correlation between thethickness of the amorphous region and at least the spectrum of cosΔ; ii)inputting at least the spectrum of the cosΔ as a measurement resultobtained by a spectroscopic ellipsometry performed on the amorphousregion formed on specific implant conditions; and iii) fetching thecorrelation and determining the thickness of the amorphous region in thesemiconductor layer by reference to the correlation about at least thespectrum of cosΔ obtained in the step ii).

In the procedure i), a relationship between implant energy and thethickness of the amorphous region and a relationship between thespectrum of cosΔ and implant energy are stored as first and secondcorrelations, respectively, with regard to each particular ion implantdose. And in the procedure iii), after the implant energy of the ionsimplanted into the semiconductor layer has been obtained by reference tothe second correlation about the spectrum of cosΔ input in the procedureii), the thickness of the amorphous region in the semiconductor layercan be determined by reference to the first correlation about theimplant energy obtained.

Alternatively, in the procedure i), a relationship between an ionimplant dose and the thickness of the amorphous region and arelationship between the spectrum of cosΔ and an ion implant dose arestored as first and second correlations, respectively, with regard toeach particular implant energy. And in the procedure iii), after theimplant dose of the ions implanted into the semiconductor layer has beenobtained by reference to the second correlation about the spectrum ofcosΔ input in the procedure ii), the thickness of the amorphous regionin the semiconductor layer can be determined by reference to the firstcorrelation about the ion implant dose obtained.

A second storage medium according to the present invention is a storagemedium used for measuring a temperature of a heat treatment conducted ona semiconductor layer in a substrate based on at least the spectrum ofcosΔ in accordance with a variation in the wavelength of measurementlight. The semiconductor layer includes an amorphous region withcrystallinity disordered by the implantation of dopant ions into thesubstrate. The measurement light has been incident on the semiconductorlayer at an angle tilted relative to p and s directions in a planevertical to the optical axis thereof and then reflected as anelliptically-polarized ray from the semiconductor layer. The p directionis defined by an intersection between the plane vertical to the opticalaxis and a plane containing incident and reflected rays. The s directionis vertical to the p direction in the plane vertical to the opticalaxis. Δ is a phase difference between p and s components as to thereflected ray. The storage medium stores a program for making a computerexecute the procedures of: i) storing a relationship between a time ofthe heat treatment and a decrease in thickness of the amorphous regionat a particular temperature as a correlation; ii) storing a thickness ofthe amorphous region prior to the heat treatment; iii) storing athickness of the amorphous region posterior to the heat treatment; andiv) fetching the thicknesses of the amorphous region measured before andafter the heat treatment is conducted and the correlation, and obtainingthe temperature of the heat treatment by reference to the correlationabout the decrease in thickness of the amorphous region before and afterthe heat treatment is conducted.

A third storage medium according to the present invention is a storagemedium used for measuring a temperature of a heat treatment conducted ona semiconductor layer in a substrate based on at least the spectrum ofcosΔ in accordance with a variation in the wavelength of measurementlight. The semiconductor layer includes an amorphous region withcrystallinity disordered by the implantation of dopant ions into thesubstrate. The measurement light has been incident on the semiconductorlayer at an angle tilted relative to p and s directions in a planevertical to the optical axis thereof and then reflected as anelliptically-polarized ray from the semiconductor layer. The p directionis defined by an intersection between the plane vertical to the opticalaxis and a plane containing incident and reflected rays. The s directionis vertical to the p direction in the plane vertical to the opticalaxis. Δ is a phase difference between p and s components as to thereflected ray. The storage medium stores a program for making a computerexecute the procedures of: i) storing a recovery rate as a correlationfor each particular temperature, the recovery rate being obtained basedon a relationship between a time of the heat treatment and a decrease inthickness of the amorphous region at each said particular temperature;ii) storing a thickness of the amorphous region prior to the heattreatment; iii) storing a thickness of the amorphous region posterior tothe heat treatment and a time of the heat treatment; and iv) fetching adecrease in thickness of the amorphous region before and after the heattreatment and the correlation, and obtaining the temperature of the heattreatment by reference to the correlation about the recovery rateobtained by dividing the decrease in thickness of the amorphous regionbefore and after the heat treatment by the time of the heat treatment.

A fourth storage medium according to the present invention is a storagemedium used for measuring a temperature of a heat treatment conducted ona semiconductor layer in a substrate based on at least the spectrum ofcosΔ in accordance with a variation in the wavelength of measurementlight. The semiconductor layer includes an amorphous region withcrystallinity disordered by the implantation of dopant ions into thesubstrate. The measurement light has been incident on the semiconductorlayer at an angle tilted relative to p and s directions in a planevertical to the optical axis thereof and then reflected as anelliptically-polarized ray from the semiconductor layer. The p directionis defined by an intersection between the plane vertical to the opticalaxis and a plane containing incident and reflected rays. The s directionis vertical to the p direction in the plane vertical to the opticalaxis. Δ is a phase difference between p and s components as to thereflected ray. The storage medium stores a program for making a computerexecute the procedures of: i) storing a recovery rate as a correlation,the recovery rate being obtained based on a relationship between atemperature of the heat treatment and a decrease in thickness of theamorphous region at a particular time; ii) storing a thickness of theamorphous region prior to the heat treatment; iii) storing a thicknessof the amorphous region posterior to the heat treatment and a time ofthe heat treatment; and iv) fetching a decrease in thickness of theamorphous region before and after the heat treatment and thecorrelation, and obtaining the temperature of the heat treatment byreference to the correlation about the recovery rate obtained bydividing the decrease in thickness of the amorphous region before andafter the heat treatment by the time of the heat treatment.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view illustrating the structure of part of asemiconductor wafer used for evaluation in an embodiment of the presentinvention.

FIG. 2 is a diagram schematically showing the arrangement of anevaluation apparatus used for the evaluation in the embodiment of thepresent invention.

FIGS. 3(a) and 3(b) are graphs illustrating the spectra of cosψ and cosΔin a low-concentration amorphous region, respectively, as data obtainedby an experiment carried out in the embodiment of the present invention.

FIGS. 4(a) and 4(b) are graphs illustrating the spectra of cosψ and cosΔin a high-concentration amorphous region, respectively, as data obtainedby an experiment carried out in the embodiment of the present invention.

FIG. 5 is a graph illustrating the spectra of cosΔ in an amorphousregion implanted with ions at a high level with the implant energythereof varied, as data obtained by an experiment carried out in theembodiment of the present invention.

FIG. 6 is a graph illustrating the spectra of tanψ in an amorphousregion implanted with ions at a high level with the implant energythereof varied, as data obtained by an experiment carried out in theembodiment of the present invention.

FIG. 7 is a graph illustrating in comparison the relationships betweenion implant energy and the thickness of an amorphous region obtained byrespective measurements according to TEM, TRIM and spectroscopicellipsometry, as data in a first specific example.

FIG. 8 is a graph illustrating the relationship between an ion implantdose and the thickness of an amorphous region obtained by a measurementaccording to spectroscopic ellipsometry, as data in the first specificexample of the first embodiment.

FIGS. 9(a) through 9(c) are diagrams for comparing the in-waferuniformity of the thickness of an amorphous region obtained by ameasurement according to spectroscopic ellipsometry as data of a secondspecific example of the first embodiment with data on the in-waferuniformity obtained according to thermal wave and sheet resistancemethods.

FIG. 10 illustrates the spectra of cosΔ and tan ψ in a singlecrystalline silicon region where no ion has been implanted, as controldata in a third specific example of the first embodiment.

FIG. 11 illustrates the spectra of cosΔ and tan ψ in an amorphous regionimplanted with ions at 1×10¹⁴ cm⁻² using an ion implanter manufacturedby company A, as data in the third specific example of the firstembodiment.

FIG. 12 illustrates the spectra of cosΔ and tan ψ in an amorphous regionimplanted with ions at 5×10¹³ cm⁻² using the ion implanter manufacturedby the company A, as data in the third specific example of the firstembodiment.

FIG. 13 illustrates the spectra of cosΔ and tan ψ in an amorphous regionimplanted with ions at 5×10¹³ cm⁻² using an ion implanter manufacturedby company B, as data in the third specific example of the firstembodiment.

FIG. 14 illustrates the spectra of cosΔ and tan ψ in an amorphous regionimplanted with ions at 1×10¹⁴ cm⁻² and a current density of 615 μA usingthe ion implanter manufactured by the company B, as data in the thirdspecific example of the first embodiment.

FIG. 15 illustrates the spectra of cosΔ and tan ψ in an amorphous regionimplanted with ions at 1×10¹⁴ cm⁻² and a current density of 2000 μAusing the ion implanter manufactured by the company B, as data in thethird specific example of the first embodiment.

FIG. 16 is a graph illustrating the relationship between a temperatureat which a wafer is held and the thickness of an amorphous region(amorphous region) in a wafer implanted with As⁺ ions as data in a firstspecific example of the second embodiment.

FIG. 17 is a graph illustrating the relationship between a temperatureat which a wafer is held and the film quality of an amorphous region(amorphous region) in a wafer implanted with As⁺ ions as data in asecond specific example of the second embodiment.

FIG. 18(a) is a graph illustrating a variation in the thickness of anamorphous region with respect to an annealing time for various samplesas data in a third specific example of the second embodiment; and FIG.18(b) is a table drawn up from the data of FIG. 18(a);

FIG. 19 is a graph illustrating the relationship between a rate at whichrecovery (recrystallization) proceeds in an amorphous region and anannealing condition described in a literature.

FIG. 20(a) illustrates data illustrating the temperature dependence of adecrease in thickness of an amorphous region (amorphous region) inaccordance with flash annealing in a fourth specific example of thesecond embodiment; and FIG. 20(b) is a graph illustrating a variation inthe thickness of an amorphous region with the passage of time whereordinary annealing is performed on the conditions for point D20 of FIG.20(a);

FIG. 21 is a diagram illustrating the distribution of thicknesses of anamorphous region in a wafer on the conditions for point A16 of FIG. 16as data in a fifth specific example of the second embodiment.

FIG. 22 is a diagram illustrating the distribution of thicknesses of anamorphous region in a wafer on the conditions for point C16 of FIG. 16as data in the fifth specific example of the second embodiment.

FIG. 23 is a diagram illustrating the distribution of temperatures in awafer obtained by subtracting a thickness at each measurement point ofFIG. 21 from a thickness at the corresponding measurement point of FIG.22 as data in the fifth specific example of the second embodiment.

FIG. 24 is a diagram illustrating the distribution of absorptioncoefficients in an amorphous region in a wafer on the conditions forpoint A16 of FIG. 16 as data in a sixth specific example of the secondembodiment.

FIG. 25 is a diagram illustrating the distribution of absorptioncoefficients in an amorphous region in a wafer on the conditions forpoint C16 of FIG. 16 as data in the sixth specific example of the secondembodiment.

FIGS. 26(a) and 26(b) are flowcharts showing the procedures ofdetermining whether or not an ion-implanted amorphous region isacceptable and modifying an ion implantation condition, respectively, ina first specific example of the third embodiment.

FIG. 27 is a flowchart showing the procedure of deriving a temperatureof a wafer surface during annealing in the second embodiment.

FIG. 28 is a flowchart showing the procedure of deriving a temperatureof a wafer surface based on a recovery rate during annealing conductedat a predetermined temperature in the second embodiment.

FIG. 29 is a flowchart showing the procedure of deriving a temperatureof a wafer surface based on a recovery rate during annealing conductedfor a predetermined period of time in the second embodiment.

FIGS. 30(a) and 30(b) are tables respectively showing first and secondcorrelations in the first specific example of the first embodiment.

FIG. 31 shows a method for obtaining the thickness of an amorphousregion by utilizing the first and second correlations where an ionimplantation dose is given in the first specific example of the firstembodiment.

FIG. 32 shows a method for obtaining the thickness of an amorphousregion by utilizing the first and second correlations where ion implantenergy is given in the first specific example of the first embodiment.

FIG. 33 is a table drawn up to list the contents of the respectivespecific examples in the respective embodiments.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 33 is a table drawn up to list the contents of the respectivespecific examples in the respective embodiments described below.

First, an evaluation method of a semiconductor for each embodimentsupporting the basic principle of the invention will be described withreference to the drawings.

FIG. 1 is a cross-sectional view illustrating the structure of asemiconductor device (an n-channel MOS transistor), to be evaluated inthe embodiment of the present invention, in an ion implantation step. Asshown in FIG. 1, in the fabrication process performed on an MOStransistor in a wafer state, an element isolation 12 is formed out of aLOCOS film on a silicon substrate (silicon wafer) 11. And a gateinsulating film 13 and a gate electrode 14 are formed in an activeregion surrounded with the element isolation 12. In the ion implantationstep, dopant ions such as As⁺ ions are implanted into the siliconsubstrate 11, whereby high-concentration source/drain regions 15 of then-channel MOS transistor are formed. In another region of the siliconsubstrate 11, a monitor region 16, used, for example, for determiningwhether or not conditions for implanting dopant ions at a high level areappropriate, is formed. And the As⁺ ions are also implanted into themonitor region 16 simultaneously with the source/drain regions 15. Informing source/drain regions for a p-channel MOS transistor, conditionsfor implanting boron ions are determined with B⁺ ions implanted intoanother monitor region.

FIG. 2 is a side view schematically illustrating the arrangement of aspectroscopic ellipsometer for determining the ion implantationconditions for the source/drain regions 15 of the n-channel MOStransistor by utilizing the monitor region 16. Xe light, output from aXe light source 20, is transformed into linearly-polarized light by apolarizer 21, and then made to be incident on the silicon substrate 11(the monitor region 16) at an angle θ₀ with respect to a normal crossingthe surface of the substrate at right angles. Light reflected as anelliptically-polarized ray is passed through an analyzer 23 and thenmade to be incident on a spectroscope 23. In this manner, a complexrefractive index N=n-ik is measured at each wavelength by a detector 24while analyzing the spectrum thereof. It is noted that the axis of theincident linearly-polarized light is tilted relative to a p direction(defined by an intersection between a plane vertical to the optical axisand a plane containing incident and reflected rays) and to an sdirection (vertical to the p direction in the plane vertical to theoptical axis).

Next, the principle of measurement according to the spectroscopicellipsometry used in this embodiment will be described. Suppose theangle formed between the Xe incident light on the silicon substrate 11and a normal crossing the silicon substrate at right angles in FIG. 2 isθ₀, then the complex refractive index N=n-ik of a sample at eachwavelength is represented by the following Equations (1) and (2):

    n.sup.2 -k.sup.2 =sin .sup.2 θ.sub.0 [1+{ tan .sup.2 θ.sub.0 (cos .sup.2 2ψ-sin .sup.2 2 ψ sin .sup.2 Δ)}/(1+sin 2ψ cos Δ).sup.2 ]                                          (1)

    2nk=(sin .sup.2 θ.sub.0 tan .sup.2 θ.sub.0 sin 4ψ sin Δ)/(1+sin 2ψ cos Δ).sup.2                 (2)

where ψ is a ratio between the amplitude reflection factors of p and scomponents, and Δ is a phase difference between the p and s components.Specifically, the complex refractive index N representing the physicalproperties of a sample at each wavelength can be obtained by derivingtanψ and cosΔ of the reflected light based on the Equations (1) and (2).

The present inventors found during the following process thatsignificant information on ion implantation conditions can be obtainedby measuring and analyzing the spectra of tan ψ and cosΔ of thereflected light without deriving the complex refractive index N itselfof a sample.

In obtaining data shown in the diagrams referred to below, a p-typesilicon substrate, already doped with a p-type dopant, is used as thesilicon substrate, the resistivity of the substrate is in the range from10.0 to 15.0 (Ω·cm) and the crystallographic orientation of the surfaceof the substrate is (100). Furthermore, As⁺ is used as implanted ionspecies, with implant energy varied in the range from 20 to 80 kev and adose varied in the range from 2 to 4×10¹⁵ cm⁻². Also, the spectrometricanalysis is conducted in the range from 250 to 800 nm.

FIGS. 3(a) and 3(b) respectively illustrate the spectra of tanψ and cosΔof the rays reflected from a silicon substrate implanted with no ionsyet (shown as a spectral line 3A in FIG. 3(b)). FIGS. 4(a) and 4(b)respectively illustrate the spectra of tan ψ and cosΔ of the raysreflected from a silicon substrate implanted with dopant ions at a highlevel. As can be understood by comparing the spectral line of cosΔhaving a valley at a wavelength of 450 nm in FIG. 4(b) with the spectralline 3A of cosΔ having a valley at a wavelength of 400 nm in FIG. 3(b),when silicon single crystals are doped with a dopant, the shape of thespectrum of cosΔ is transformed, so that the valley tends to be locatedin a longer-wavelength region (in the range from 450 nm to about 850nm), and corresponds to a smaller negative value. Therefore, it is clearthat the spectra of tan ψ and cosΔ are changed by the ion implantation.

Furthermore, in general, as shown in FIG. 3(b), once the silicon singlecrystals are doped with a dopant, as the dose is increased, the spectrumof cosΔ tends to shift from the spectral line 3A, corresponding to thenon-implantation, toward the negative domain (spectral lines 3B and 3C)to reach a smaller value. Accordingly, by obtaining tan ψ and cosΔ at agiven wavelength (e.g., 630 nm) for a single crystalline siliconsubstrate, the conditions for the ion implantation such as a dose can beestimated to a certain degree.

FIG. 5 illustrates the change of the spectral shapes of cosΔ inaccordance with the variation in the implant energy for an amorphoussilicon layer, and FIG. 6 illustrates the change of the spectral shapesof tan ψ in accordance with the variation in the implant energy for anamorphous silicon layer. The dose of dopant ions (As⁺) is 4×10¹⁵ cm⁻².

As can be understood from FIGS. 5 and 6, in implanting ions into anamorphous silicon layer, the ion implant energy cannot be derived fromthese measurement results even if tan ψ and cosΔ are obtained at a givenwavelength (e.g., 630 nm), because there is no regularity in thevariation of the values of tanψ and cosΔ in accordance with the increaseof the implant energy.

As described above, in accordance with the conventional technique, it isimpossible to determine by the ellipsometry whether or not theconditions such as ion implant energy are appropriate as to an impuritydiffusion region formed by implanting dopant ions at a high level.

EMBODIMENT 1

Hereinafter, specific examples will be described as exemplaryinformation obtained by the spectroscopic ellipsometry.

Specific Example 1

In this specific example, a method of determining the thickness of anamorphous region (or an "ion implanted region", so to speak) byreference to a correlation about the spectrum of cosΔ (or tan ψ)obtained by the spectroscopic ellipsometry will be described. In thisspecification and claims, a "spectrum" may be understood as a spectralpattern or as (a table of) values of cosΔ (or tan ψ) relative towavelengths.

In obtaining data shown in FIGS. 7 and 8, a p-type silicon substrate,already doped with a p-type dopant, is used as the silicon substrate,the resistivity thereof is in the range from 10.0 to 15.0 (Ω·cm) and thecrystallographic orientation of the surface of the substrate is (100).Furthermore, As⁺ is used as implanted ion species, with implant energyvaried in the range from 20 to 80 keV and a dose varied in the rangefrom 2 to 4×10¹⁵ cm⁻². The spectrometric analysis is conducted in therange from 250 to 800 nm.

FIG. 7 illustrates data representing the dependence of the thickness ofan amorphous region on the implant energy where the implant dose is heldat a constant value of 4×10¹⁵ cm⁻². In FIG. 7, the axis of abscissasindicates the implant energy (keV) and the axis of ordinates indicatesthe thickness of the amorphous region (nm). The data shown in FIG. 7 isobtained by measuring the thicknesses of amorphous regions for theimplant energy conditions shown in FIGS. 5 and 6 (i.e., 20, 30, 40 and50 kev) in accordance with TEM and by finding correlations between theresultant spectral shapes of cosΔ and tan ψ and the measured thicknessesof the amorphous regions. FIG. 7 also shows the relationship between theimplant energy and the thickness of an amorphous region obtained inaccordance with TEM. As can be understood FIG. 7, the thickness of theamorphous region obtained by the spectroscopic ellipsometry of thisembodiment approximates the thickness actually measured with TEM, andthus, precise measurement can be performed nondestructively. In otherwords, an evaluation method suitable for an in-line test (which is atest carried out between processes as shown in FIG. 20) can be provided.

FIG. 8 shows data representing the dependence of the thickness of anamorphous region on the implant dose where the ion implant energy isheld at a constant value of 40 keV. In FIG. 8, the axis of abscissasindicates the implant dose (×10¹⁵ cm⁻²) and the axis of ordinatesindicates the thickness of an amorphous region (nm). The data of FIG. 8is obtained by measuring the thicknesses of amorphous regions inaccordance with TEM with the implanted dose (dose) varied at five stepsof 2.0, 2.5, 3.0, 3.5 and 4.0×10¹⁵ cm⁻², and by finding correlationsbetween the spectral shapes of cosΔ and tan ψ and the measuredthicknesses of the amorphous regions.

FIG. 30(a) is a matrix in which the thicknesses d11, d12, d13, etc. ofamorphous regions, each obtained with the implant dose D fixed and theimplant energy E varied at values E1, E2, E3, etc., are correlated withvarious implant doses D1, D2, D3, etc. The relationship between theimplant energy E and the thickness d of an amorphous region, shown inthis matrix and obtained with the ion implant dose fixed, will beregarded as a first correlation. The first correlation can berepresented as the dependence of the thickness of an amorphous region onthe implant energy shown in FIG. 7.

Alternatively, the matrix shown in FIG. 30(a) may be regarded as a tablein which the thicknesses d11, d21, d31, etc., each obtained with theimplant energy E fixed and the implant dose D varied at values D1, D2,D3, etc., are correlated with implant energy values E1, E2, E3, etc. Insuch a case, the relationship between the implant dose D and thethickness d of an amorphous region, shown in this matrix and obtainedwith the ion implant energy fixed, is the first correlation. This firstcorrelation can be represented as the dependence of the thickness of anamorphous region on the implant dose as shown in FIG. 8.

FIG. 30(b) is a matrix in which the spectral patterns of cosΔ (or anumerical relationship between a measurement wavelength and cosΔ), eachobtained with the implant dose D fixed and the implant energy E variedat values E1, E2, E3, etc., are correlated with various implant dosesD1, D2, D3, etc. The relationship shown in this matrix between theimplant energy E and the spectrum of cosΔ will be regarded as a secondcorrelation.

Alternatively, the matrix shown in FIG. 30(b) may be regarded as a tablein which the spectra of cosΔ, each obtained with the implant energy Efixed and the implant dose varied at values D1, D2, D3, etc., arecorrelated with various implant energy values E1, E2, E3, etc. In such acase, the relationship between the implant energy and the spectrum ofcosΔ, shown in this matrix and obtained at a constant implant dose D, isregarded as the second correlation.

In this specific example, by using the data shown in FIGS. 5, 7, 8,30(a) and 30(b), the thickness of an amorphous region can be obtained bythe following methods.

In a first method, which is the simplest, the spectral pattern of cosΔ(or tan ψ) (or a numerical relationship between a measurement wavelengthand cosΔ), obtained by performing a measurement on an amorphous regionin accordance with the spectroscopic ellipsometry, is referred to therelationships between cosΔ (or tan ψ) and wavelengths on variousimplantation conditions shown in FIG. 30(b) (i.e., the secondcorrelation), thereby choosing the most matched one and determining thethickness of the amorphous region. In this method, either the spectralshape or the table of correspondence between the wavelength values andthe values of cos Δ may be used. In accordance with this method,attention is focused on the point that, once ions implanted aredetermined, a unique spectral shape of cosΔ (or tan ψ) can be obtainedfrom an implant dose or energy. When the spectral shape is used, afingerprint identification system may be applied, for example.

In a second method, which is shown in FIG. 31, the thickness of anamorphous region is obtained by utilizing the first and secondcorrelations when an implant dose for the ion implantation is known.

First, in Step ST61, the thicknesses d of amorphous regions, eachobtained with the implant dose D fixed and the implant energy E variedat values E1, E2, E3, etc., are derived in accordance with TEM for eachof various implant doses D1, D2, D3, etc. These relationships are storedas the first correlations shown in FIG. 30(a).

Next, in Step ST62, the relationships between the spectra of cosΔ,obtained from an amorphous region formed at a constant implant dose, andthe implant energy E are established and stored as the secondcorrelation shown in FIG. 30(b).

Then, in Step ST63, the spectral pattern of cosΔ is obtained byperforming a measurement according to the spectroscopic ellipsometry onan amorphous region formed at a known implant dose. A table ofcorrespondence between the wavelength values and the value of cosΔ maybe drawn up instead. For example, suppose a spectral pattern SA5 shownin FIG. 5 is herein obtained.

Next, in Step ST64, the spectral pattern SA5 is referred to the secondcorrelation, thereby obtaining the implant energy E. In the exampleshown in FIG. 5, the implant energy E resulting in the spectral patternSA5 is assumed to be 35 keV, for example.

Then, in Step ST65, the implant energy E obtained is referred to thefirst correlation, thereby determining the thickness d of the amorphousregion. For example, if the implant energy E has been turned out to be35 keV, the thickness of the amorphous region can be determined as 62 nmby reference to the table of FIG. 30(b) or FIG. 7. In general, thethickness of an amorphous region may be defined by approximately every 5nm, and this thickness of the amorphous region may be approximated at 60nm. In practice, if arrangements are made so that the thickness can becalculated based on the data actually measured by the ellipsometry asshown in FIG. 7, the thickness of an amorphous region can be calculatedinstantaneously by this method through computation based on the measureddata within an apparatus in the same manner as in the first method. Itis clear that the result of calculation substantially accords with thevalue actually measured by TEM.

In a third method, which is shown in FIG. 32, the thickness of anamorphous region is obtained by using the first and second correlationswhen implant energy for the ion implantation is known.

First, in Step ST71, the thicknesses d of amorphous regions, eachobtained with the implant energy E fixed and the implant dose varied atvalues D1, D2, D3, etc., are derived in accordance with TEM for each ofvarious implant energy values E1, E2, E3, etc. These relationships arestored as the first correlations.

Next, in Step ST72, the relationships between the spectra of cosΔ,obtained from an amorphous region formed at constant implant energy, andthe implant dose are drawn up and stored as the second correlation shownin FIG. 30(b).

Then, in Step ST73, the spectral pattern of cosΔ is obtained byperforming a measurement according to the spectroscopic ellipsometry onan amorphous region formed at known implant energy. A table ofcorrespondence between the wavelength values and the value of cosΔ maybe drawn up instead.

Next, in Step ST74, the spectral pattern of cosΔ is referred to thesecond correlation, thereby obtaining the implant dose D.

Then, in Step ST75, the implant dose D obtained is referred to the firstcorrelation, thereby determining the thickness d of the amorphousregion. That is to say, the thickness of the amorphous region can bedetermined by reference to the table of FIG. 30(b) or FIG. 8. Inpractice, if arrangements are made so that the thickness can becalculated based on the data actually measured by the ellipsometry asshown in FIG. 8, the thickness of an amorphous region can be calculatedinstantaneously by this method through computation based on the measureddata within an apparatus in the same manner as in the first method.

In a fourth method, the dependence of the thickness of an amorphousregion on the implant energy shown in FIG. 7 is combined with therelationship between the implant energy and the spectral shape shown inFIG. 5. In a predetermined wavelength region in the spectrum of cosΔ ofthe reflected light, the thickness of an amorphous region can besubstantially estimated if the wavelength corresponding to a localmaximum of the spectrum is known. If the first correlation isestablished in the same manner as in the second method and if therelationship between the wavelength corresponding to the local maximumand the implant energy E is stored as the second correlation for eachion implant dose, the thickness of an amorphous region can be obtainedwith ease through a similar procedure to that of the flowchart shown inFIG. 31.

In a fifth method, the dependence of the thickness of an amorphousregion on the implant dose shown in FIG. 8 is combined with therelationship between the implant dose and the spectral pattern shown inFIG. 3(b). In a predetermined wavelength region in the spectrum of cosΔof the reflected light, the thickness of an amorphous region can besubstantially estimated if the wavelength corresponding to a localmaximum of cosΔ in the spectrum is known. If the first correlation isestablished in the same manner as in the third method and if therelationship between the local maximum of cosΔ and the implant energy Eis stored as the second correlation for each ion energy, the thicknessof an amorphous region can be obtained with ease through a similarprocedure to that of the flowchart shown in FIG. 32.

Specific Example 2 (In-Plane Distribution of Thicknesses of AmorphousRegions)

FIGS. 9(a), 9(b) and 9(c) are diagrams illustrating the in-wafer-planeuniformities of amorphous regions obtained by performing measurementsaccording to spectroscopic ellipsometry, thermal wave method and sheetresistance method, respectively, on the same wafer. These diagrams showresults of measurement on the conditions that As⁺ is implanted atimplant energy of 40 keV and an implant dose of 5×10¹⁵ cm⁻². Inaccordance with the spectroscopic ellipsometry according to thisembodiment shown in FIG. 9(a), the thickness of the amorphous region is69 nm and the in-plane uniformity is 0.153%. In FIG. 9(a), a portionshown with symbols (-) having a reduced thickness corresponds to theamorphous region. FIG. 9(b) shows the in-plane uniformity of an ionimplant dose in accordance with the thermal wave method, in which aportion shown with symbols (□) corresponds to a region with an averagevalue. FIG. 9(c) shows the in-plane uniformity of an ion implant dose inaccordance with the sheet resistance method. In each of these drawings,a contour line corresponds to a boundary between areas with a differenceof 0.5%. Herein, a value obtained by the thermal wave method is merely arelative quantity, and it cannot be determined whether or not the valueaccurately accords with the ion implant dose. In the data shown in FIG.9(c), the in-plane uniformity of the ion implant dose is very poor. Whenthe sheet resistance measurement is employed, a heat treatment isrequired for activating the implanted impurity in order to measure thesheet resistance, and it seems that the in-plane uniformity has beendegraded through this heat treatment.

In contrast, although the method for measuring the in-plane uniformityof the thickness of an amorphous region by spectroscopic ellipsometry ofthis embodiment is nondestructive, variation in thickness of theamorphous region in the wafer plane can be analyzed as a variationresulting from implantation conditions alone, not involved with a factorconcerning a heat treatment.

Specific Example 3

The present specific example relates to information derived from thecharacteristic shapes of spectral lines of tan ψ and cosΔ measured bythe spectroscopic ellipsometry of this invention.

FIG. 10 shows the spectral lines of tan ψ and cosΔ obtained byperforming the spectroscopic ellipsometry on a silicon substrate notimplanted with dopant ions. FIGS. 11 through 15 show the spectral linesof tan ψ and cosΔ obtained by performing the spectroscopic ellipsometryon regions in silicon substrates implanted with dopant ions onrespective conditions shown in these drawings.

The spectral line of cosΔ of FIG. 10 for the silicon substrate notimplanted with a dopant includes three characteristic regions Ra, Rb andRc. The region Ra is a decreasing region where the spectral line changesdiagonally down to the right. The region Rb is a local minimum regionhaving a certain width where the value of cosΔ reaches a local minimum.The region Rc is an increasing region where the spectral line changesdiagonally up to the right. Also, the decreasing region Ra ischaracterized by a hump portion Rh. By comparing the shapes of thesecharacteristic regions in the respective diagrams with the shapes of thespectral lines of cosΔ and tan ψ obtained by the spectroscopicellipsometry after the ion implantation, the following information areobtained:

(1) Difference in the shape of spectral line owing to difference indose:

The relationship between a difference in implant dose and a differencein the spectral shape of cosΔ obtained by using the same implanter willnow be discussed. Comparing FIGS. 11 and 12 with each other, thegradient of the spectral line of cosΔ in the decreasing region Ra isgentler in FIG. 11, and the hump portion Rh to be observed in thedecreasing region Ra is more indistinct in FIG. 11. While the humpportion Rh distinctly appears in the spectral line of cosΔ of theundoped substrate as shown in FIG. 10, the hump portion Rh does notdistinctly appear in FIG. 11. This means that an amorphous region can beformed in a silicon substrate more easily on the conditions of FIG. 11,i.e., when the implant dose of dopant ions is larger. Similarly,comparing FIGS. 13 and 14 with each other, the gradient in thedecreasing region Ra is gentler and the hump portion Rh is moreindistinct in FIG. 14 using the conditions with a larger ion implantdose, and thus, the same conclusion can be derived.

(2) Comparison between the performances of implanters:

Comparing FIGS. 12 and 13 with each other, the hump portion Rh of thespectral line in the decreasing region Ra is more indistinct and thegradient in the increasing region Rc is gentler in FIG. 13. As shown inFIG. 10, in the spectral line of cosΔ of the undoped substrate, the humpportion Rh appears more distinctly and the gradient in the increasingregion Rc is steeper. Since the ion implantation conditions for FIGS. 12and 13 are the same except for the types of implanters, it can beunderstood that an amorphous region can be more easily formed in asilicon substrate by the ion implanter manufactured by company B. Inother words, in accordance with the method of this embodiment, theperformance of an ion implanter can be evaluated.

(3) Current density dependency:

Comparing FIGS. 14 and 15 with each other, the gradients of the spectralline in the decreasing and increasing regions Ra, Rc are slightlygentler in FIG. 14 than in FIG. 15. This can be understood because, forexample, the value of cosΔ at the wavelength of 300 nm in FIG. 14 issmaller than the value of cosΔ at the same wavelength in FIG. 15.Accordingly, an amorphous region is less likely to be formed in asilicon substrate on the conditions for FIG. 15. Comparing theconditions for FIGS. 14 and 15 with each other, the only differencetherebetween is that a current density is larger in the conditions forFIG. 15. Specifically, if the ion implantation is performed with largecurrent as in FIG. 15, a so-called beam anneal effect in which anamorphous region tries to recover its crystallinity in response to theion implantation is generated.

Comparing FIGS. 11 and 15 with each other about this current densitydependency, although these spectra are both obtained at the same ionimplant dose, the hump portion Rh is more distinct and the gradient inthe decreasing region Ra is slightly steeper in FIG. 11 than in FIG. 15.Furthermore, the local minimum region Rb is flat in FIG. 11, where theamorphous region has a smaller thickness. These results tell that theion implanter of company A exhibits greater beam anneal effect than theion implanter of company B using the implantation conditions with acurrent density of 2000 μA. It is noted that the current density of theion implanter of company A is unknown.

(4) Other information:

For example, comparing FIGS. 10, 11 and 12 with one another, it can beunderstood that the crystallinity is disordered to a larger degree (moreamorphous) as the spectral shape of tan ψ is gentler. Accordingly,taking the spectral shape of tan ψ into consideration as well as thespectral shape of cosΔ, the ion implantation conditions and the physicalquantity of an amorphous region can be more accurately determined thanconsidering only the spectral shape of cosΔ. However, since the spectralpattern of cosΔ includes a larger number of characteristic regions andis varied to a larger degree depending upon the ion implantationconditions, it is generally sufficient to observe the spectral patternof cosΔ alone.

In each of the aforementioned specific examples, As⁺ ions are implantedas the dopant ions. However, the present invention is not limited tothese specific examples. Alternatively, this invention is applicable toa semiconductor layer to which B⁺ ions, Si⁺ ions, P⁺ ions or the likehave been implanted. Furthermore, the semiconductor layer is notnecessarily a silicon layer, but may be a semiconductor layer made ofany other semiconductor material such as a compound semiconductor.

EMBODIMENT 2

Next, the second embodiment, relating to the application ofspectroscopic ellipsometry to the measurement of an actual temperatureon a substrate surface during a process such as annealing, will bedescribed.

Specific Example 1 (Method for Measuring Actual Temperature on SubstrateSurface)

First, the relationship between an annealing process and the thicknessof an amorphous region is obtained.

FIG. 16 shows data illustrating the relationship between the temperatureat which a wafer is held and the thickness of an amorphous region whereAs⁺ ions have been implanted into the wafer at 30 keV and 3×10¹⁴ cm⁻².The axis of abscissas indicates the power of the power supply of adegassing chamber, which is 0% in OFF State and 100% at the maximum. Thedegassing chamber is a chamber attached to a CVD system or a sputteringsystem, and a wafer is heated and retained in vacuum in the degassingchamber. The power of the degassing chamber is indicated as 0 through100% in this manner, but the surface temperature of the substrate placedin the chamber cannot be accurately known. The axis of ordinatesindicates the thickness of an amorphous region measured after a samplehas been retained at a predetermined temperature. A wafer including asemiconductor layer to which As⁺ ions have been implanted and adegassing chamber for pre-heating provided to a Ti sputtering system areused, and the substrate is heated in vacuum in the chamber. Also, thethickness of the amorphous region is measured in the same manner asdescribed with reference to FIGS. 7 and 8. Specifically, the thicknessesof an amorphous region are measured on the conditions corresponding topoints A16, B16 and C16 by performing the spectroscopic ellipsometry onthe amorphous region. The amorphous region is retained in the degassingchamber for 30 sec. in each case, and a so-called TC wafer, providedwith a temperature sensor on its back surface, is used for measuring thetemperature. However, with the TC wafer, only the temperature on theback surface of the wafer can be measured and the temperature on the topsurface thereof cannot be known. The point A16 in FIG. 16 corresponds toa state where the wafer has been retained in the degassing chamber forthe time of "0", i.e., the data about an "as-implanted" sample. Thepoint B16 corresponds to the data obtained when the power supplied tothe degassing chamber reaches 40% of the rated power (the temperature onthe back surface measured on the TC wafer is 250° C.) The point C16corresponds to the data obtained when the power supplied to thedegassing chamber reaches 60% of the rated power (the temperature on theback surface is 270° C.). And the point D16 corresponds to the dataobtained when the power supplied to the degassing chamber reaches 70% ofthe rated power (the temperature on the back surface is 350° C.). Whenannealing is conducted at such a low temperature, the thickness does notchange so much but does decrease in 30 sec.

FIG. 19 corresponds to FIG. 4 described in a literature (Journal ofApplied Physics Vol. 48, No. 10, October 1977, p. 4237), illustratingthe relationship between a recovery (recrystallization) rate of anamorphous region and an annealing condition. In FIG. 19, the axis ofabscissas indicates the temperature, and the axis of ordinates indicatesthe rate of recovery from amorphous state to crystalline state. As canbe understood from this diagram, the recovery rate of an amorphousregion formed by implanting, for example, As ions is approximately 60Å/min. at 500° C. As shown in FIG. 19, it is known that there is adefinite correlation between the annealing temperature and the recovery.However, no data is provided for the recovery rate at a temperatureequal to or lower than 450° C.

In an amorphous region formed by implanting, for example, As⁺ ions at1×10¹⁵ cm⁻², it has been considered that the amorphous region does notrecover (or is recrystallized) if the annealing temperature is equal toor lower than approximately 450° C. On the other hand, according to thedata shown in FIG. 16, a decrease in thickness of the amorphous regionis observed even if the annealing is conducted at as low a temperatureas about 250° C. to about 350° C., and hence, it was confirmed that anamorphous region recovers (or is recrystallized) to some degree even atsuch a low temperature.

Conventionally, the temperature within a chamber is measured with atemperature sensor provided on the back surface of a TC wafer. However,although the temperature on the back surface of a wafer can be sensedusing a TC wafer, the temperature on the top surface of the wafer, i.e.,the actual temperature at which an amorphous region is subjected to theheat treatment cannot be measured. Also, the range of the temperaturesmeasurable with a TC wafer is limited, and it is said that themeasurement accuracy is degraded when the temperature reaches a certainhigh point (in the range from 500 to 600° C. or more).

In contrast, according to the method of this specific example, thetemperature on the top surface of a wafer can be precisely measured byusing the correlation between the holding time and the recovery rate orbetween the holding time and a decrease in thickness to be used in thespecific examples described below. Accordingly, even in an apparatus inwhich merely a percentage of the power supplied is indicated as in thedegassing chamber, the surface temperature of a wafer associated withparticular power supplied can be accurately measured. The surfacetemperature of a wafer cannot be known based on the experiment dataalone. But if the thicknesses before and after the heat treatment areknown by using the thickness measurement described in the firstembodiment, the temperature during the heat treatment can be estimatedbased on the correlation between the holding time and the recovery rateor between the holding time and a decrease in thickness. Specificmethods thereof will be described later.

In this specific example, the measurement of the temperature on the topsurface of a wafer placed in a degassing chamber has been described.Alternatively, the temperature on the top surface of a wafer can also beaccurately measured in a similar manner in any other apparatus such as aCVD system, a sputtering system and an annealing system. Furthermore,since the temperature on the top surface of a wafer can be measured, thedistribution of temperatures in a wafer plane or in a region where thewafer is placed within the chamber can be also sensed.

Specific Example 2

Next, the results of an experiment performed in a second specificexample for finding the relationship between an annealing condition andthe film quality of an amorphous region (amorphous region) will bedescribed.

FIG. 17 shows data illustrating the relationship between the temperatureat which a wafer is held and the absorption coefficient of lightincident on an amorphous region. In FIG. 17, the conditions of thewafer, the retaining time in the degassing chamber and the like are thesame as those adopted in measuring the thickness shown in FIG. 16. Apoint A17 in FIG. 17 corresponds to the data in the state where thewafer has been retained in the degassing chamber for the time of "0",i.e., the data about an "as-implanted" sample. A point B17 correspondsto the data obtained when the power supplied to the degassing chamberreaches 40% of the rated power (the back surface temperature is 250°C.). A point C17 corresponds to the data obtained when the powersupplied to the degassing chamber reaches 60% of the rated power (theback surface temperature is 270° C.). And a point D17 corresponds to thedata obtained when the power supplied to the degassing chamber reaches70% of the rated power (the back surface temperature is 350° C.). InFIG. 17, each parenthesized temperature is the temperature measured witha temperature sensor attached to a TC wafer. The absorption coefficientdoes not change so much but to a certain degree in 30 sec.

It was found from the results of the experiment shown in FIG. 17 that adifference in the film quality of an amorphous region depending on anannealing condition can also be estimated. Although it takes a certaintime to observe spectral shapes obtained by the spectroscopicellipsometry, if the absorption coefficient alone is to be obtained, thefilm quality can be evaluated very quickly and easily. The absorptioncoefficient depends upon the transparency of an amorphous region andreflects the crystallographic state of an amorphous region. Accordingly,a range of absorption coefficients, which is not likely to result indefective products, may be defined and prepared beforehand as anappropriate range during a fabrication process. Then, it can bedetermined very rapidly during an actual fabrication process whether ornot a product is acceptable. Specifically, if the absorption coefficientof an amorphous region is within the appropriate range, then theresulting product will be acceptable. Alternatively, if the absorptioncoefficient is out of the appropriate range, then the resulting productwill be defective.

Specific Example 3

Next, a third specific example, relating to the correlation betweenvariations in the thickness and absorption coefficient of an amorphousregion (amorphous region) during annealing and a holding time obtainedby measuring the thickness in accordance with the spectroscopicellipsometry, will be described.

FIG. 18(a) shows data illustrating variations in thickness andabsorption coefficient with an annealing time for various samples. InFIG. 18(a), the variation in thickness of a wafer, to which ions havebeen implanted at 30 keV and 4×10¹⁵ cm⁻², is represented with ∘, thevariation in absorption coefficient of a wafer, to which the ions havebeen implanted under the same condition, is represented with , thevariation in thickness of a wafer, to which the ions have been implantedat 30 keV and 3×10¹⁴ cm⁻², is represented with Δ, and the variation inabsorption coefficient of a wafer, to which the ions have been implantedunder the same condition, is represented with ▴. All the samples areheld at a temperature of 550° C. for a predetermined period of time.

Based on the gradients of the lines respectively linking the data shownwith ∘ and Δ, the following observations can be made.

With regard to the data shown with Δ, the variation in thickness fromthe start of annealing until 10 seconds have passed is (44.8-32) nm/10sec.=77 nm/min. This recovery (recrystallization) rate is much largerthan the recovery rate of 20 nm/min. at a temperature of 550° C.(corresponding to a point X) shown in FIG. 19. The recovery rate in 50seconds from a point in time 10 seconds have passed since the start ofthe annealing until a point in time 60 seconds have passed is (32-15)nm/50 sec.=17 nm/50 sec.=20.4 /min. This value is substantially equal tothe recovery rate of 20 nm/min. at 550° C. shown in FIG. 19. Therecovery rate in 120 seconds from a point in time 60 seconds have passeduntil a point in time 180 seconds have passed is 15/120 (sec.)=7.5nm/min., which is very small. Thereafter, at a point in time 120 secondshave passed, the amorphous region has already disappeared.

With regard to the data shown with ∘, the variation in recovery rate issubstantially equal to that of the data shown with Δ. It should benoted, however, in an amorphous region formed by implantinglow-concentration ions at a dose as low as 3×10¹⁴ cm⁻², the recoveryproceeds with the passage of annealing time and the thickness ultimatelybecomes substantially "0". In contrast, the thickness of an amorphousregion formed by implanting high-concentration ions at a dose as high as4×10¹⁵ cm⁻² is substantially constant after 50 seconds have passed. Inother words, after about 50 seconds have passed, the recovery hardlyproceeds. This phenomenon probably has something to do with the amountof residual oxygen.

Furthermore, with regard to the data shown with  and ▴, the variationsare comparatively similar to those of the data shown with ∘ and Δ. Thismeans that not only the variation in film quality but also the variationin thickness can be analyzed to a certain degree by observing the valuesof the absorption coefficient.

FIG. 18(b) is a table in which the annealing time, the thickness of theamorphous region and the recovery rate obtained from the data shown inFIG. 18(a) (the annealing at 550° C.) are listed. This table is drawn upfor the data shown with Δ, but a similar table can be drawn up for thedata shown with ∘. If a table such as that shown in FIG. 18(b) isprepared for each of various annealing temperatures, an annealingtemperature can be determined based on the recovery rate and the holdingtime.

In this manner, according to this specific example, the variation in therate of recovery from the amorphous state to the crystalline state withthe passage of time can be obtained at a predetermined annealingtemperature, and an annealing temperature can be also sensed.

Specific Example 4

Next, a fourth specific example for finding the relationship between theannealing temperature and the variation in thickness along with therecovery of an amorphous region (amorphous region), similar to the datashown in FIG. 19, during low-temperature annealing conducted at 550° C.or less, inter alia at 450° C. or less, will be described.

FIG. 20(a) shows the data illustrating the dependence of a recovery rateof an amorphous region on the temperature where flash annealing has beenconducted with the holding time set at substantially "0". That is tosay, annealing is conducted on a wafer under a condition where the powersupply is turned off immediately after the temperature has increased.The data in FIG. 20(a) is obtained in a wafer implanted with As⁺ ions at30 keV and 3×10¹⁴ cm⁻². As shown in FIG. 20(a), it can be seen that thedecrease in thickness resulting from the recovery of the amorphousregion varies substantially linearly with the annealing temperature. Asfor the recovery of an amorphous region (amorphous region) formed underthe conditions shown in FIG. 20(a), the lower the annealing temperatureis, the more remarkably the recovery tends to slow down, even if theannealing time is extended any more.

In FIG. 20(a), points B20, C20, D20, E20 and F20 respectively correspondto annealing at 250° C., 270° C., 350° C., 450° C. and 550° C. At thesepoints, the recovery thicknesses of the amorphous region are 0.4 nm, 1.8nm, 2.8 nm, 6.2 nm and 9 nm, respectively. At the three points B20, C20and D20, the annealing temperature is so low that a unique phenomenonoccurs in the recovery from the amorphous state to the crystallinestate.

FIG. 20(b) is a graph illustrating the variation in thickness of anamorphous region with the passage of time where ordinary annealing isperformed under the conditions of the point D20. As shown in FIG. 20(b),even if the amorphous region is retained for a long period of time underthe conditions of the point D20 after the thickness thereof hasdecreased by 2.8 nm in a very short period of time, the crystallizationdoes not proceed any longer and the thickness of the amorphous regionremains constant. The similar phenomenon is observed during ordinaryannealing under conditions of the points B20 and C20. Specifically,while the annealing temperature is low, the thickness of the amorphousregion immediately decreases but the crystallization does not proceedthereafter. Suppose an amorphous region, formed by implanting, forexample, As⁺ ions at 30 keV and 3×10¹⁴ cm⁻² is retained for a desiredperiod of time in a system for conducting a process at a temperatureequal to or lower than 450° C., at which the recovery from the amorphousstate to the crystalline state is less likely to proceed, and thedecrease in thickness of the amorphous region before and after theprocess is obtained. Then, the accurate annealing temperature can beestimated based on the data of FIG. 20(a) by utilizing this phenomenon.

If the data as shown in FIG. 20(a) is previously obtained for amorphousregions (specifically, such as source/drain regions in a MOSFET) formedunder various ion implantation conditions, an annealing temperature canalso be estimated in the low temperature annealing at 450° C. or lowerbased on the thicknesses of the amorphous regions measured by theellipsometry. For example, under the conditions for flash annealing, ifthe thickness of the amorphous region has changed by about 6 nm beforeand after the annealing, the annealing temperature would beapproximately 440° C.

Specifically, by utilizing such a measurement result, an actualannealing temperature can be estimated by reference to such data aboutactual thickness variation and processing conditions. Furthermore, basedon such data, the annealing conditions can be set accurately.

Moreover, annealing may be conducted with constant heating power, andthe correlation between the temperature and the thickness may beobtained by using the heating power as a parameter.

With regard to annealing conducted at a temperature of 450° C. or morefor a comparatively short period of time, an annealing temperature canbe estimated based on the recovery rate obtained from the decrease inthickness of an amorphous region measured with an ellipsometer and theannealing time by using the data shown in FIG. 19. However, the recoverystate of an amorphous region is variable with the ion implantationconditions and the annealing temperatures as shown in FIG. 18.Accordingly, the data shown in FIG. 19 is not always suitable foraccurate measurement of a temperature. Thus, it is preferred that thetemperature dependence of the decrease in thickness of an amorphousregion as shown in FIG. 20 is previously obtained for various ionimplantation conditions. In particular, if the annealing time isvariable, then it is preferably defined beforehand how the thickness ofan amorphous region varies with the passage of annealing time as shownin FIG. 18.

Next, by utilizing the data described in the first through fourthspecific examples, the temperature can be measured in the followingmanner.

FIG. 27 is a flowchart illustrating the procedure for determining atemperature on the surface of a wafer during annealing by utilizing thedata of FIG. 20.

First, in Step ST31, an amorphous region with a thickness d0 is formed.Next, in Step ST32, a heat treatment (annealing) is conducted at apredetermined temperature T for a certain period of time t, and theresultant thickness d1 of the amorphous region is measured. Then, inStep ST33, the decrease d0-d1 in thickness of the amorphous region iscalculated. Finally, in Step ST34, the calculated decrease is comparedwith the decrease shown in FIG. 20, thereby determining thepredetermined temperature T.

FIG. 28 is a flowchart illustrating the procedure for determining thetemperature on the surface of a wafer based on the recovery rate duringannealing at a predetermined temperature by utilizing the data in FIG.18.

First, in Step ST41, an amorphous region with a thickness d0 is formed.Next, in Step ST42, a heat treatment (annealing) is conducted at apredetermined temperature T with the given time t varied at t1, t2 andt3, and the resultant thicknesses d1, d2 and d3 of the amorphous regionare measured. Then, in Step ST43, the recovery rates r (=d0-d1/t1,d0-d2/t2 and d0-d3/t3) of the amorphous region are calculated. Finally,in Step ST44, the recovery rate in FIG. 18 (or FIG. 19) is compared withthe calculated recovery rates r, thereby determining the predeterminedtemperature T. Also, since the thickness at any point in times can befound in comparing the recovery rates, the annealing temperature canalso be determined by utilizing FIG. 18(a) if the decrease in thicknessof the amorphous region is known. For example, if the initial thicknessis found 44.8 nm and the thickness after the annealing has beenconducted for 10 seconds is found 32 nm as a result of the measurement,the annealing temperature can be determined at 550° C. with reference tothe prepared data such as that shown in FIG. 18(a) about variousannealing temperatures.

FIG. 29 is a flowchart illustrating the procedure for determining thetemperature on the surface of a wafer based on a recovery rate duringannealing conducted for a certain period of time by preparing the datasuch as that shown in FIG. 18 for various annealing temperatures.

First, in Step ST51, an amorphous region with a thickness d0 is formed.Next, in Step ST52, a heat treatment (annealing). is conducted for acertain period of time t with the predetermined temperature varied atT1, T2 and T3, and the resultant thicknesses d1, d2 and d3 of theamorphous region are measured. Then, in Step ST53, the recovery rates r(=d0-d1/t, d0-d2/t and d0-d3/t) of the amorphous region are calculated.Finally, in Step ST54, among a large number of data about the recoveryrates as show n FIG. 18, a temperature corresponding to a recovery rate,which is most matched with the calculated recovery rate r, is selected,thereby determining the predetermined temperature T.

Specific Example 5

Next, a fifth specific example relating to the measurement of thedistribution of temperatures within a wafer or a chamber using thespectroscopic ellipsometry will be described.

FIG. 21 is a thickness distribution diagram illustrating the in-planeuniformity of an amorphous region in a wafer placed in the state of thepoint A16 of FIG. 16. In this state, the average thickness is 44.785 nm,which is equal to the thickness at the point A16 of FIG. 16. Thethickness at each point in the wafer is indicated to be larger (shownwith +) or smaller (shown with -) than the average thickness. FIG. 22 isa thickness distribution diagram in an amorphous region in a waferplaced in the state of the point C16 of FIG. 16. In the same way as inFIG. 21, the thickness at each point in the wafer is indicated to belarger (shown with +) or smaller (shown with -) than the averagethickness. In this state, the average thickness is 43.059 nm, which isequal to the thickness at the point C16 of FIG. 16. It can be seen thatthe thickness distribution shown in FIG. 22 is completely different fromthe thickness distribution of FIG. 21. FIG. 23 is a diagram illustratingthe distribution of values, each obtained by subtracting the thicknessat each measurement point shown in FIG. 21 from the thickness at thecorresponding point shown in FIG. 22, and shows the variation inthickness at each point in 30 seconds. The decrease in thicknesscorresponds to a thickness changed from the amorphous state to thecrystalline state, and it is shown how the decreases are distributedwith respect to the average thickness (shown with a bold line) in thewafer plane.

The distribution of temperatures in a wafer plane can be derived byobtaining the distribution of decreases in thickness. Speaking morespecifically, the annealing time is 30 seconds, and since the variationin average thickness can be obtained by subtracting the thickness at C16(43.059 nm) from the thickness at A16 (44.785 nm), the decrease inthickness is (44.758-43.059)=1.726 nm. Accordingly, based on the data inFIG. 20, the annealing temperature can be obtained (275° C. in thiscase), and at the same time, the distribution of temperatures in thewafer plane can be derived from the distribution of the decreases inthickness in the wafer plane.

Specific Example 6

Next, a sixth specific example relating to the measurement of thedistribution of film qualities in a wafer or a chamber using thespectroscopic ellipsometry will be described.

FIG. 24 is a diagram illustrating the distribution of absorptioncoefficients in an amorphous region in a wafer placed in the state ofthe point A16 of FIG. 16. If an amorphous region has a large absorptioncoefficient, then the transparency thereof is necessarily high. That isto say, though the region is still amorphous, the region is closer to acrystalline state. Thus, the film quality of an amorphous region can bedetermined based on the absorption coefficient. There are various levelsof amorphous states including one with a smaller degree of irregularityand closer to a crystalline state and one with a larger degree ofirregularity and highly amorphous. Accordingly, the film quality is usedas an index for distinguishing the difference. FIG. 25 is a diagramillustrating the distribution of absorption coefficients in an amorphousregion in a wafer placed in the state of the point C16 of FIG. 16.

In this specific example, the distribution of the recovery states of thefilm quality in an amorphous region as a result of annealing can bederived from the distribution of absorption coefficients. Specifically,it is conventionally impossible to evaluate the in-plane uniformity inthe recovery states of the film quality in an amorphous region as aresult of low temperature annealing. However, according to the presentinvention, the in-plane uniformity of the film qualities in an amorphousregion can be evaluated.

By utilizing the values or the in-wafer-plane distribution of absorptioncoefficients, the film quality of a region where silicide is formed(source/drain regions of an MOS transistor), for example, can beevaluated.

For example, since the film quality of an underlying semiconductor layer(source, drain or gate region) affects the reactivity in silicidation ina salicide process, it is significant to know the film quality of thesemiconductor layer before the silicidation is performed. Accordingly,before a titanium film is deposited on an ion-implanted semiconductorlayer (e.g., source/drain regions), the absorption coefficient of thesemiconductor layer is measured, and the relationship between theabsorption coefficient and the grain size of a silicide subsequentlyformed or the development of the silicidation is found beforehand. Then,the silicidation process can be appropriately controlled.

EMBODIMENT 3

In this embodiment, a method of controlling a fabrication process byutilizing the first embodiment or the first to sixth specific examplesof the second embodiment will be described.

Specific Example 1

FIGS. 26(a) and 26(b) are flowcharts illustrating two methods ofcontrolling an ion implantation step by utilizing the measurement of thethickness of an amorphous region according to the first embodiment.

In the method shown in FIG. 26(a), a substrate including a semiconductorlayer is cleaned in Step ST11, and an amorphous region is formed in thesemiconductor layer by implanting ions into the semiconductor layer inStep ST12. Next, in Step ST13, it is determined whether or not thethickness of the amorphous region falls within an appropriate range. Ifit is determined that the thickness of the amorphous region is withinthe appropriate range, the procedure proceeds to the next step ST14,where a heat treatment is conducted for activating the ions.Alternatively, if it is determined in Step ST13 that the thickness ofthe amorphous region is out of the appropriate range, the substrate isremoved from the lot.

In accordance with this method, it is possible to avoid uselessprocessing, which would other be performed on a defective substratesubsequently.

In accordance with the method shown in FIG. 26(b), a substrate includinga semiconductor layer is cleaned in Step ST21, and an amorphous regionis formed in the semiconductor layer by implanting ions into thesemiconductor layer in Step ST22. Next, in Step ST23, it is determinedwhether or not the thickness of the amorphous region falls within anoptimal range requiring no modification to the implantation conditions.If it is determined that the thickness of the amorphous region fallswithin the optimal range, the procedure proceeds to the next step ST24without taking any action, where a heat treatment is conducted foractivating the ions. Alternatively, if it is determined in Step ST23that the thickness of the amorphous region is out of the optimal range,the implantation conditions for Step ST22 are modified so that thethickness of the amorphous region falls within the optimal range (byincreasing the implant energy).

In accordance with this method, it is possible to retain the ionimplantation conditions for the ion implantation step as optimal aspossible. As a result, the yield can be improved, and subsequentprocedures can be stabilized because the variation in thickness of theamorphous regions can be suppressed.

Alternately, it may be determined in Step ST23 whether or not thethickness of the amorphous region is equal to or larger than a lowerlimit. If the thickness of the amorphous region is equal to or largerthan the lower limit, the procedure may proceed to the next step ST24.Conversely, if the thickness of the amorphous region is smaller than thelower limit, the procedure may return to step ST22, where ions areadditionally implanted.

Specific Example 2

In this specific example, a method of controlling a film deposition stepwill be described. In this case, the following two methods areavailable.

In a first method, after a polysilicon film, a metal film, an insulatingfilm or the like is deposited over an amorphous region in a substrate byCVD or sputtering, the film is removed by wet etching, for example. Thespectroscopic ellipsometry is conducted before and after CVD orsputtering is performed, and the thicknesses of the amorphous region arecompared before and after the process. In this manner, the temperatureor the distribution of temperatures during CVD or sputtering can bederived. If the underlying amorphous region is affected during theremoval of the film, an error, generated in the data because of theeffect on the underlying amorphous region, may be corrected by repeatingexperiments. Specifically, the etched thickness of the amorphous regioncan be calculated based on an etching rate at which the amorphous regionis removed. The etched thickness of the amorphous region may beconfirmed by repeating the experiment several times and subtracted,whereby an accurate temperature for CVD or sputtering can be detected.

In a second method, if a film to be formed is transparent to measurementlight (e.g., a silicon oxide or silicon nitride film), then thethickness of an amorphous region is measured with the transparent filmformed on the amorphous region (i.e., in the shape of a two-layeredfilm). In this manner, a temperature on the surface of a substrateduring the film deposition is sensed.

Conventionally, there is no effective means for sensing a temperature onthe surface of a substrate during CVD or sputtering. However, byutilizing the first to sixth specific examples of the second embodiment,a temperature on the surface of a substrate can be sensed for varioustypes of CVD ranging from high temperature CVD to low temperature CVD.Accordingly, it is possible to properly set a temperature forappropriately retaining the temperature for CVD, specifically, plasmapower and the like. Also, the distribution of temperatures within achamber can also be sensed during CVD.

In any of the first and second methods, the data in FIG. 19 may be usedif a high temperature heat treatment is involved.

Furthermore, in ashing a resist, the temperature rises to about 300° C.Accordingly, the temperature can be sensed based on the measuredthickness of an amorphous region.

OTHER EMBODIMENTS

The measurement of the thickness and film quality of an amorphous regionand an annealing temperature described in the foregoing embodiments canbe automatically conducted by storing the procedures thereof in astorage medium.

For example, by storing the procedures of the first to fifth methodsdescribed in the first specific example of the first embodiment (such asthe procedures shown in FIGS. 31 and 32) as a program in a computerreadable storage medium, the thickness of an amorphous region formed byion implantation can be automatically detected.

Alternatively, if the procedures for measuring a temperature byutilizing the thickness of an amorphous region described in the secondembodiment (such as the procedures shown in FIGS. 27 through 29) arestored as a program in a computer readable storage medium, a temperaturecan be automatically detected during a process.

INDUSTRIAL APPLICABILITY

The present invention is applicable to the fabrication of semiconductordevices such as various types of transistors and semiconductor memoriesincorporated into electronic units.

What is claimed is:
 1. An evaluation method of a semiconductor layer,comprising the steps of:i) making linearly-polarized measurement lightincident on the surface of the semiconductor layer at a tilt angledefined with respect to a normal crossing the surface at right angles,the semiconductor layer including an amorphous region with crystallinitydisordered by dopant ions implanted into a substrate, the measurementlight being tilted relative to p and s directions in a plane vertical tothe optical axis thereof, the p direction being defined by anintersection between the plane vertical to the optical axis and a planecontaining incident and reflected rays, the s direction being verticalto the p direction in the plane vertical to the optical axis; ii)deriving at least cosΔ as to the reflected ray of the measurement lightreflected as an elliptically-polarized ray from the semiconductor layer,where Δ is a phase difference between p and s components; iii) measuringa spectrum of at least the cosΔ variable with a variation in thewavelength of the measurement light; and iv) estimating a physicalquantity of the amorphous region based on at least the spectrum of thecosΔ.
 2. The evaluation method of a semiconductor layer of claim 1,further comprising the step of calculating a reflection factor of themeasurement light reflected from the amorphous region based on a ratiobetween the intensity of the incident ray and that of the reflected rayof the measurement light,wherein a film quality of the amorphous regionis evaluated based on the reflection factor.
 3. The evaluation method ofa semiconductor layer of claim 1, wherein in the step iv), it isdetermined whether or not the amorphous region is present.
 4. Theevaluation method of a semiconductor layer of claim 1, wherein in thestep iv), the thickness of the amorphous region is detected.
 5. Theevaluation method of a semiconductor layer of claim 4, furthercomprising the step of preparing a a correlation between at least thespectrum of cosΔ and the thickness of the amorphous region,wherein inthe step iv), the thickness of the amorphous region in the semiconductorlayer is determined by reference to the correlation about at least thespectrum of cosΔ obtained in the step ii).
 6. The evaluation method of asemiconductor layer of claim 5, wherein, in the step of preparing thecorrelation, a relationship between implant energy and the thickness ofthe amorphous region and a relationship between the spectrum of cosΔ andimplant energy are prepared as first and second correlations,respectively, with regard to each particular ion implant dose,andwherein in the step iv), after the implant energy of the ionsimplanted into the semiconductor layer has been obtained by reference tothe second correlation about the spectrum of cosΔ obtained in the stepii), the thickness of the amorphous region in the semiconductor layer isdetermined by reference to the first correlation about the implantenergy obtained.
 7. The evaluation method of a semiconductor layer ofclaim 5, wherein, in the step of preparing the correlation, arelationship between an ion implant dose and the thickness of theamorphous region and a relationship between the spectrum of cosΔ and anion implant dose are prepared as first and second correlations,respectively, with regard to each particular implant energy, andwhereinin the step iv), after the implant dose of the ions implanted into thesemiconductor layer has been obtained by reference to the secondcorrelation about the spectrum of cosΔ obtained in the step ii), thethickness of the amorphous region in the semiconductor layer isdetermined by reference to the first correlation about the ion implantdose obtained.
 8. The evaluation method of a semiconductor layer ofclaim 5, wherein, in the step of preparing the correlation, arelationship between implant energy and the thickness of the amorphousregion is prepared as a first correlation with regard to each particularion implant dose, and a relationship between a wavelength correspondingto a local maximum of cos Δ within a predetermined wavelength region ofthe spectrum of cosΔ and implant energy is prepared as a secondcorrelation, the wavelength region being defined by making the ionimplant dose constant and the implant energy variable, andwherein in thestep iv), after the implant energy of the ions implanted into thesemiconductor layer has been obtained by reference to the secondcorrelation about the spectrum of cosΔ obtained in the step ii), thethickness of the amorphous region in the semiconductor layer isdetermined by reference to the first correlation about the implantenergy obtained.
 9. The evaluation method of a semiconductor layer ofclaim 5, wherein, in the step of preparing the correlation, arelationship between an implant dose and the thickness of the amorphousregion is prepared as a first correlation with regard to each particularimplant energy, and a relationship between a wavelength corresponding toa local maximum of cos Δ within a predetermined wavelength region of thespectrum of cosΔ and an implant dose is prepared as a secondcorrelation, the wavelength region being defined by making the implantenergy constant and the implant dose variable, andwherein in the stepiv), after the implant dose of the ions implanted into the semiconductorlayer has been obtained by reference to the second correlation about thespectrum of cosΔ obtained in the step ii), the thickness of theamorphous region in the semiconductor layer is determined by referenceto the first correlation about the ion implant dose obtained.
 10. Theevaluation method of a semiconductor layer of claim 4, wherein thedistribution of thicknesses of a plurality of amorphous regions in thesemiconductor layer is measured by performing the steps i) through iv)on the amorphous regions in the semiconductor layer.
 11. The evaluationmethod of a semiconductor layer of claim 1, wherein, in the step iv),the degree of recovery of the amorphous region responsive to ion beamsis estimated.
 12. The evaluation method of a semiconductor layer ofclaim 1, wherein, in the step iv), the performance of implanters areevaluated based on at least the spectra of cosΔ of two amorphous regionsformed using two different implanters on the same implant conditions.13. The evaluation method of a semiconductor layer of claim 1, furthercomprising the steps of:deriving tan ψ as to the reflected ray of themeasurement light, where ψ is a ratio of the amplitude of a p componentto that of an s component; and measuring the spectrum of the tan ψ withthe wavelength of the measurement light varied, wherein, in the step ofestimating the physical quantity of the amorphous region, the physicalquantity of the amorphous region is estimated with the shape of thespectrum of the tan ψ taken into consideration.
 14. The evaluationmethod of a semiconductor layer of claim 4, wherein, a first thicknessof the amorphous region is determined by performing the steps i) throughiv) on the semiconductor layer before a heat holding process isconducted,the method further comprising the steps of:determining asecond thickness of the amorphous region by performing the steps i)through iv) on the semiconductor layer after the heat holding processhas been conducted on the semiconductor layer; and measuring atemperature of the heat holding process based on a recovery rate derivedfrom the first and second thicknesses of the amorphous region and a timeof the heat holding process.
 15. The evaluation method of asemiconductor layer of claim 14, further comprising the step of findinga correlation between a temperature of the heat holding processconducted at a temperature equal to or lower than 450° C. and a decreasein thickness of an amorphous region,wherein, in the step iv), thetemperature of the heat holding process is measured based on thecorrelation.
 16. The evaluation method of a semiconductor layer of claim14, wherein the temperature of the heat holding process is measured asto each of a plurality of amorphous regions in the substrate, andwhereinthe distribution of temperatures in the substrate or in a processingsystem is measured based on the temperatures held at the amorphousregions.
 17. A method for fabricating a semiconductor device on asemiconductor layer in a substrate, the method comprising the stepsof:i) forming an amorphous region with crystallinity disordered byimplanting dopant ions into the semiconductor layer; ii) makinglinearly-polarized measurement light incident on the surface of thesemiconductor layer, where the amorphous region has been formed, at atilt angle defined with respect to a normal crossing the surface atright angles, the measurement light being tilted relative to p and sdirections in a plane vertical to the optical axis thereof, the pdirection being defined by an intersection between the plane vertical tothe optical axis and a plane containing incident and reflected rays, thes direction being vertical to the p direction in the plane vertical tothe optical axis, and measuring at least the spectrum of cosΔ inaccordance with a variation in the wavelength of the measurement lightas to the reflected ray of the measurement light reflected as anelliptically-polarized ray from the semiconductor layer, where Δ is aphase difference between p and s components; and iii) estimating aphysical quantity of the amorphous region based on at least the spectrumof the cosΔ obtained in the step ii).
 18. The method for fabricating asemiconductor device of claim 17, further comprising the step ofpreparing a correlation between the thickness of the amorphous regionand at least the spectrum of cosΔ,wherein, in the step iii), thethickness of the amorphous region in the semiconductor layer isdetermined by reference to the correlation about at least the spectrumof cos Δ obtained in the step ii).
 19. The method for fabricating asemiconductor device of claim 18, further comprising the step ofchanging ion implantation conditions for the step ii) based on theresult of evaluation of the physical quantity of the amorphous regionobtained in the step iii).
 20. The method for fabricating asemiconductor device of claim 18, further comprising the step ofdetermining whether or not the substrate including the amorphous regionis acceptable based on the result of evaluation of the physical quantityof the amorphous region obtained in the step iii).
 21. A method forfabricating a semiconductor device on a semiconductor layer in asubstrate, the method comprising the steps of:i) forming an amorphousregion with crystallinity disordered by implanting dopant ions into thesemiconductor layer; ii) conducting a process of holding the temperatureof the amorphous region at a predetermined temperature; iii) makinglinearly-polarized measurement light incident on the surface of thesemiconductor layer at a tilt angle defined with respect to a normalcrossing the surface at right angles, the measurement light being tiltedrelative to p and s directions in a plane vertical to the optical axisthereof, the p direction being defined by an intersection between theplane vertical to the optical axis and a plane containing incident andreflected rays, the s direction being vertical to the p direction in theplane vertical to the optical axis, and measuring at least the spectrumof cosΔ in accordance with a variation in the wavelength of themeasurement light as to the reflected ray of the measurement lightreflected as an elliptically-polarized ray from the semiconductor layer,where Δ is a phase difference between p and s components; and iv)estimating a physical quantity of the amorphous region based on at leastthe spectrum of cosΔ obtained in the step iii).
 22. The method forfabricating a semiconductor device of claim 21, further comprising thestep of preparing a correlation between the thickness of the amorphousregion and at least the spectrum of cosΔ,wherein, in the step iv), thethickness of the amorphous region in the semiconductor layer isdetermined by reference to the correlation about at least the spectrumof cosΔ obtained in the step ii).
 23. The method for fabricating asemiconductor device of claim 22, further comprising the stepsof:estimating the thickness of the amorphous region prior to the stepii) by performing the same process steps as the steps iii) and iv)posterior to the step i) and prior to the step ii); and obtaining avariation in the thickness of the amorphous region before and after thestep ii) is performed.
 24. The method for fabricating a semiconductordevice of claim 21, wherein in the step iv), a reflection factor of themeasurement light reflected from the amorphous region is calculatedbased on a ratio between the intensity of the incident and reflectedrays of the measurement light, and film quality of the amorphous regionis evaluated based on the reflection factor.
 25. A method forfabricating a semiconductor device on a semiconductor layer in asubstrate, the method comprising the steps of:i) forming an amorphousregion with crystallinity disordered by implanting dopant ions into thesemiconductor layer; ii) conducting a process of holding the temperatureof the amorphous region at a predetermined temperature; iii) makinglinearly-polarized measurement light incident on the surface of thesemiconductor layer at a tilt angle defined with respect to a normalcrossing the surface at right angles, the measurement light being tiltedrelative to p and s directions in a plane vertical to the optical axisthereof, the p direction being defined by an intersection between theplane vertical to the optical axis and a plane containing incident andreflected rays, the s direction being vertical to the p direction in theplane vertical to the optical axis, and measuring at least the spectraof cosΔ before and after the process in the step ii) is performed as tothe reflected ray of the measurement light reflected as anelliptically-polarized ray from the semiconductor layer, where Δ is aphase difference between p and s components; iv) measuring a variationin the thickness of the amorphous region before and after the process inthe step ii) is performed based on at least the variation in thespectrum of cosΔ; and v) measuring a temperature of the heat holdingprocess based on a recovery rate calculated based on the variation inthe thickness of the amorphous region before and after the process isperformed and a time of the heat holding process.
 26. The method forfabricating a semiconductor device of claim 25, further comprising thestep of preparing a correlation between a temperature of the heatholding process conducted at a temperature equal to or lower than 450°C. and a decrease in thickness of the amorphous region,wherein, in thestep iv), the temperature of the heat holding process is measured basedon the correlation.
 27. A computer readable storage medium used forestimating a physical quantity of an amorphous region based on at leastthe spectrum of cosΔ in accordance with a variation in the wavelength ofmeasurement light, the amorphous region being located in a semiconductorlayer in a substrate, the crystallinity of the amorphous region havingbeen disordered by the implantation of dopant ions into the substrate,the measurement light having been incident on the semiconductor layer atan angle tilted relative to p and s directions in a plane vertical tothe optical axis thereof and having been reflected as anelliptically-polarized ray from the semiconductor layer, the p directionbeing defined by an intersection between the plane vertical to theoptical axis and a plane containing incident and reflected rays, the sdirection being vertical to the p direction in the plane vertical to theoptical axis, Δ being a phase difference between p and s components asto the reflected ray,the storage medium storing a program for making acomputer execute the procedures of:i) storing a correlation between thethickness of the amorphous region and at least the spectrum of cosΔ; ii)inputting at least the spectrum of the cosΔ as a measurement resultobtained by a spectroscopic ellipsometry performed on the amorphousregion formed on specific implant conditions; and iii) fetching thecorrelation and determining the thickness of the amorphous region in thesemiconductor layer by reference to the correlation about at least thespectrum of cosΔ obtained in the step ii).
 28. The storage medium ofclaim 27, wherein, in the procedure i), a relationship between implantenergy and the thickness of the amorphous region and a relationshipbetween the spectrum of cosΔ and implant energy are stored as first andsecond correlations, respectively, with regard to each particular ionimplant dose, andwherein in the procedure iii), after the implant energyof the ions implanted into the semiconductor layer has been obtained byreference to the second correlation about the spectrum of cosΔ input inthe procedure ii), the thickness of the amorphous region in thesemiconductor layer is determined by reference to the first correlationabout the implant energy obtained.
 29. The storage medium of claim 27,wherein, in the procedure i), a relationship between an ion implant doseand the thickness of the amorphous region and a relationship between thespectrum of cosΔ and an ion implant dose are stored as first and secondcorrelations, respectively, with regard to each particular implantenergy, andwherein in the procedure iii), after the implant dose of theions implanted into the semiconductor layer has been obtained byreference to the second correlation about the spectrum of cosΔ input inthe procedure ii), the thickness of the amorphous region in thesemiconductor layer is determined by reference to the first correlationabout the ion implant dose obtained.
 30. A computer readable storagemedium used for measuring a temperature of a heat treatment conducted ona semiconductor layer in a substrate based on at least the spectrum ofcosΔ in accordance with a variation in the wavelength of measurementlight, the semiconductor layer including an amorphous region withcrystallinity disordered by the implantation of dopant ions into thesubstrate, the measurement light having been incident on thesemiconductor layer at an angle tilted relative to p and s directions ina plane vertical to the optical axis thereof and having been reflectedas an elliptically-polarized ray from the semiconductor layer, the pdirection being defined by an intersection between the plane vertical tothe optical axis and a plane containing incident and reflected rays, thes direction being vertical to the p direction in the plane vertical tothe optical axis, Δ being a phase difference between p and s componentsas to the reflected ray,the storage medium storing a program for makinga computer execute the procedures of:i) storing a relationship between atime of the heat treatment and a decrease in thickness of the amorphousregion at a particular temperature as a correlation; ii) storing athickness of the amorphous region prior to the heat treatment; iii)storing a thickness of the amorphous region posterior to the heattreatment; and iv) fetching the thicknesses of the amorphous regionmeasured before and after the heat treatment is conducted and thecorrelation, and obtaining the temperature of the heat treatment byreference to the correlation about the decrease in thickness of theamorphous region before and after the heat treatment is conducted.
 31. Acomputer readable storage medium used for measuring a temperature of aheat treatment conducted on a semiconductor layer in a substrate basedon at least the spectrum of cosΔ in accordance with a variation in thewavelength of measurement light, the semiconductor layer including anamorphous region with crystallinity disordered by the implantation ofdopant ions into the substrate, the measurement light having beenincident on the semiconductor layer at an angle tilted relative to p ands directions in a plane vertical to the optical axis thereof and havingbeen reflected as an elliptically-polarized ray from the semiconductorlayer, the p direction being defined by an intersection between theplane vertical to the optical axis and a plane containing incident andreflected rays, the s direction being vertical to the p direction in theplane vertical to the optical axis, Δ being a phase difference between pand s components as to the reflected ray,the storage medium storing aprogram for making a computer execute the procedures of:i) storing arecovery rate as a correlation for each particular temperature, therecovery rate being obtained based on a relationship between a time ofthe heat treatment and a decrease in thickness of the amorphous regionat each said particular temperature; ii) storing a thickness of theamorphous region prior to the heat treatment; iii) storing a thicknessof the amorphous region posterior to the heat treatment and a time ofthe heat treatment; and iv) fetching a decrease in thickness of theamorphous region before and after the heat treatment and thecorrelation, and obtaining the temperature of the heat treatment byreference to the correlation about the recovery rate obtained bydividing the decrease in thickness of the amorphous region before andafter the heat treatment by the time of the heat treatment.
 32. Acomputer readable storage medium used for measuring a temperature of aheat treatment conducted on a semiconductor layer in a substrate basedon at least the spectrum of cosΔ in accordance with a variation in thewavelength of measurement light, the semiconductor layer including anamorphous region with crystallinity disordered by the implantation ofdopant ions into the substrate, the measurement light having beenincident on the semiconductor layer at an angle tilted relative to p ands directions in a plane vertical to the optical axis thereof and havingbeen reflected as an elliptically-polarized ray from the semiconductorlayer, the p direction being defined by an intersection between theplane vertical to the optical axis and a plane containing incident andreflected rays, the s direction being vertical to the p direction in theplane vertical to the optical axis, Δ being a phase difference between pand s components as to the reflected ray,the storage medium storing aprogram for making a computer execute the procedures of:i) storing arecovery rate as a correlation, the recovery rate being obtained basedon a relationship between a temperature of the heat treatment and avariation in thickness of the amorphous region at a particular time; ii)storing a thickness of the amorphous region prior to the heat treatment;iii) storing a thickness of the amorphous region posterior to the heattreatment and a time of the heat treatment; and iv) fetching a decreasein thickness of the amorphous region before and after the heat treatmentand the correlation, and obtaining the temperature of the heat treatmentby reference to the correlation about the recovery rate obtained bydividing the decrease in thickness of the amorphous region before andafter the heat treatment by the time of the heat treatment.
 33. Theevaluation method of a semiconductor layer of claim 15, wherein thetemperature of the heat holding process is measured as to each of aplurality of amorphous regions in the substrate, andwherein thedistribution of temperatures in the substrate or in a processing systemis measured based on the temperatures held at the amorphous regions.